The achilles' heel of the U.S. Constitution are political parties. The model of government the U.S. Constitution established was designed to forge a republic of “United States” from southern and northern states, within the context of slavery. The Constitution was not written to address and mitigate the power of political parties and thus I see the possibility of a constitutionally enabled dictatorship.
How would a constitutionally enabled dictatorship look like? First, you neuter the electoral college. Next, you remove all power from the minority party in Congress. Next, you have 60% of the U.S. Senate made up of party of the President and more than half of the House also the same party as the President. Finally, you have all Supreme Court justices of the same party as the president. All three branches align to one party and then Congress and the Supreme Court do nothing more than rubber stamp anything the President requests and you have in place a dictatorship.
The Supreme Court is not supposed to be political but it now totally is ever since the Reagan administration.
The Congress is supposed to be the primary means of checks and balances but that too has turned into nothing more than alignment with the President since Vietnam.
The fourth estate, the press, is now corporately owned and no longer fulfills its defacto role in government given to it by the first amendment.
And finally, we seem to no longer really have U.S. Citizens, instead we are people who see themselves as Conservative or Liberal, Republican or Democrat.
You don’t need a civil war. Democracy in the U.S. will fail without a single shot fired no matter the interpretation of the second amendment.